Rotary heat exchanging drums are widely used in the paper, fabric and web making industries. A plurality of heat exchanging drums sequentially contact the web engaging the drum's periphery to transfer heat between the drum and web. In many instances, steam is introduced into the drums through a rotary joint and condenses upon the drum shell inner wall and the condensate is removed through the same or another rotary joint. In some web forming operations cool water may be introduced into the drum to cool the web being processed.
A heat exchanging drum will be subjected to a wide range of temperatures. During start up the drum may be cold, i.e. at room temperature. Pressurized steam is introduced into the drum through the rotary joint, and it is important that the seals of the rotary joint be effective under all temperature conditions to provide a fluid tight seal regardless of the temperature of the joint or drum. Due to the thermal expansion and contraction of the drum, which may be significant, the axial dimension of the drum, and its associated supporting shafts and journals, will significantly vary under the different temperatures to which the drum is exposed. As the rotary joint is mounted at the end of the drum journal the axial dimensional variation of the drum journal often negatively affects the effectiveness of the rotary joint seals as the joint seals often utilize axial forces and pressures to produce sealing. Hence, under "cold" conditions the rotary joint seal surfaces may not be as effective as under "hot" operating conditions unless thermal compensating constructions are utilized, and under hot operating conditions axial expansion may produce excessive seal pressures.
While it is known to design rotary joints for drum type heat exchangers having thermal seal compensating features, known thermal compensating designs are relatively limited in the degree of axial compensation that may be accommodated, and a need exists for a rotary joint capable of effectively functioning under a wide range of thermal conditions.
It is an object of the invention to provide a rotary joint for use with rotary drum type heat exchangers which is capable of accommodating large axial dimensional variations due to thermal expansion and contraction.
Another object of the invention is to provide a rotary joint for rotary heat exchangers wherein a combination of axial and radial seals are utilized to provide effective fluid tight sealing under a wide range of temperatures.
An additional object of the invention is to provide a rotary joint capable of accommodating significant axial dimensional variations which is self-aligning with respect to the heat exchanger drum axis of rotation and is capable of maintaining a fluid tight connection even though eccentricities exist between the axes of the rotating heat exchanging drum and the rotary joint housing.
Yet another object of the invention is to provide a rotary joint capable of effectively operating under a wide range of thermal conditions and the joint sealing structure remains effective throughout the operating range of the joint.
In the practice of the invention a mounting flange is concentrically mounted upon the end of the journal of a rotating heat exchanger drum or the like. A wear plate is, in turn, mounted upon the flange, and the wear plate includes a seal surface concentric with the central passage which extends through the wear plate and the mounting flange.
The rotary joint housing is supported upon rods in a conventional manner, and the housing includes a cylindrical chamber substantially coaxially related to the axis of drum rotation. A generally cylindrical nipple is axially displaceable within the housing chamber and an end cap mounted upon an end of the housing includes seals which interconnect the housing and nipple in a fluid tight manner, yet permit the nipple to be axially displaced with respect to the housing and chamber.
The exterior end of the nipple abuts against an annular seal ring which engages the wear plate seal surface, and keying means interposed between the housing end cap and nipple cause the nipple to be rotatably fixed with respect to the housing.
In the disclosed embodiment a single fitting is mounted upon the housing in communication with the chamber to permit a heat exchanging medium to be introduced into the chamber, or removed therefrom, and the axially moveable relationship between the housing and nipple permits extensive axial displacement between the nipple and housing to occur without adversely affecting the efficiency of the rotary joint seals.
Preferably, a plurality of compression springs interposed between the housing and nipple bias the nipple toward the wear plate and seal ring to insure engagement between the nipple, seal ring and wear plate under all conditions.
The components of a rotary joint in accord with the invention are relatively simple in configuration permitting economical construction and assembly, and a rotary joint constructed in accord with the inventive concepts may be installed by those having average skill in the art.